Michael Clarke's strained hamstring in Hobart gave the first hint this year that he is human. Alastair Cook might not be, given the new England captain doesn't sweat - not even on the subcontinent, where he has just led his team to its first series win in India in 28 years.

Fitness permitting, Clarke has a chance during the Boxing Day test against Sri Lanka to break Ricky Ponting's record for the most runs by an Australian in a calendar year. It would be a crowning achievement for a remarkable year, but perhaps not a defining one, given the reputations of Clarke and Cook will be shaped largely by their first exchanges as captains during next year's back-to-back Ashes contests.

They are contrasting characters. The Australian's exuberance shines through in his batting. Though the Englishman is not so aesthetically pleasing, as India's bowlers discovered he can be almost impossible to get out.

Clarke comes from Sydney's working class west, while Cook was educated at a prestigious school and is happiest mucking about at his wife's farm in Bedfordshire.

Both were earmarked for great things at a young age, and both have pinned their success on hard work, Clarke subjecting himself to boot camps with his personal trainer and Cook lugging bricks through the woods in Essex under the guidance of his mentor and batting coach Graham Gooch.

The new Ashes captains have stepped out of the shadows of respected, even revered figures, in Ponting and Andrew Strauss. But Clarke and Cook have one major thing in common - captaincy has made them better.

''With certain people, they are able to rise to that little bit of added pressure,'' says Ponting, whose most prolific year, 2005, was his second as captain, but included the first of two Ashes defeats in England.

''A lot of the other guys, probably a lot of the subcontinental better players who have become captains, haven't been able to deal with the added pressure that goes with the captaincy and being a top-order batter. When you take over there's so much more importance placed on your time and you can worry about everyone else and neglect your own game, but he has taken his own preparation to a new level.''

Cook has scored five centuries in six tests as captain. Since accepting the job from Strauss, he has accumulated 562 runs in four tests in India, at an average of 80.20 with three impressive centuries in the first three matches.

His work was not confined to the middle. Cook inherited a side that had been beaten at home by South Africa and fallen out with Kevin Pietersen. But he kept the team together after the first test was lost in Ahmedebad, while Pietersen came back into the dressing room without much drama.

That Cook coped so admirably with such a daunting first assignment did not surprise Strauss, who in an interview with former England paceman Angus Fraser for The Independent said Cook had started the transformation from plodder to more expansive cricketer when he took over as one-day captain.

''I think when you take over as captain, mindset-wise, it really helps you. You are obviously determined to lead from the front and to set the right example. You walk a bit taller and you know you are unlikely to be dropped any time soon. It puts you in a good mindset to go out there and to make the most of any good form you have,'' said Strauss, whose captaincy was distinguished by two Ashes victories.

''He [Cook] has an incredible temperament for test cricket. He is very calm. He doesn't look too far ahead. He literally does play the game one ball at a time.

''He has a great defensive technique and there is no ego to his game. In his batting there is a complete lack of emotion, which is perfect.''

Cook is so cool he revealed after making 148 in searing Adelaide heat in 2010 that he sweats so little he didn't need to change his gloves.

''Underneath there must be a lot of emotion but he allows his mind to control any nerves, frustration or fire in his belly,'' said Strauss.

''He will not get carried away and it is great to see him do what he is doing because how you start your reign as captain does have a huge effect on how people view you.''

Like Cook, Clarke has convinced a sceptical nation that he is up to the task of captaining Australia.

In 19 matches as captain, Clarke has plundered 2107 runs at an average of 70.23 and scored a century in every completed series except last autumn's tour of the Caribbean.

There, he revealed himself as a captain who was prepared to take a risk to win, declaring behind in Barbados.

Three double centuries and his dazzling 329 not out to begin the year at the SCG have Clarke poised to surpass his predecessor Ponting's mark of 1544 runs in a calendar year, set in 2005.

Clarke's 1489 runs in 2012 have come at an astonishing average of 106.36.

''A little bit of extra responsibility seems to have sat really well with him and being in control of your own game, being able to play the way you want to play, makes the captaincy side of things seem that little bit easier.

''We've had some pretty good results since Michael has taken over and Cook has been exactly the same, since he's taken over he hasn't put a foot wrong,'' said Ponting.

As the recently retired champion knows, Ashes series bring new pressures, and shape reputations.

''Cook seems like a pretty calculated sort of bloke, he's pretty quiet , but a very successful player so he obviously understands his game and the game well,'' Ponting said.

''The fact that he can go on his test series to India and win and play the way he has says a lot about him, it says he will stand up to the pressure of an Ashes series as captain.

''The South African series we have just played, as far as the hype goes and the level of cricket ... is what you'd expect from an Ashes series so I think Michael will be better off for having been through that.''